The present invention relates to a flat panel display such as a plasma display panel (abbreviated to xe2x80x9cPDPxe2x80x9d), and more specifically to a flat panel display having an improved structure for mounting on a panel a driver IC (integrated circuit) for driving display cells.
A PDP is generally constituted of a front transparent plate (glass plate) and a rear transparent plate (glass plate) bonded to each other to interpose therebetween a partition for confining a number of display cells, a rare gas being sealed within a display cell space confined by the partition and the front and rear transparent plates. On the front glass plate, a number of transparent scan electrodes and transparent sustain electrodes are located in parallel to one another, and on the rear glass plate, a number of data electrodes are located in parallel to one another, orthogonally to the scan electrodes and the sustain electrodes. By applying respective predetermined voltages to these three kinds of cell electrodes at predetermined timings, an electric discharge is generated between the electrodes, so that ultraviolet is generated by the electric discharge, with the result that a phosphor coated in the display cells generates a visible light in response to the generated ultraviolet. In a color display, different phosphors for respectively generating three primary colors of red, green and blue, are used in different display cells, so that the display cells are selectively driven for light generation, with the result that a desired color image can displayed.
As mentioned above, in order to cause the PDP to emit light from the respective display cells, it is necessary to supply the voltages to the respective electrodes at predetermined timings. For this purpose, a driver IC is required to be integrally mounted in the PDP.
Referring to FIG. 8, there is shown a partially broken, diagrammatic perspective view of a PDP apparatus 200 including a PDP module 1 having driver ICs mounted thereon. A PDP 10 included in the PDP module 1, has a front glass plate 11 and a rear glass plate 12 bonded to each other, as mentioned above. A reinforcement plate 14 formed of for example aluminum is integrally mounted to a rear surface of the PDP 10. This reinforcement plate 14 mechanically reinforces the PDP 10, and also can be used as a mounting plate when the PDP module 1 is mounted within a casing 201, in order to constitute the PDP apparatus 200.
A display window 202 is formed in a front face of the casing 201, and a protection plate 203 formed of for example a transparent acrylic resin, is mounted on the display window. The driver ICs mounted on the PDP 10 are located at a periphery of the PDP 10, in such a manner that scan side driver ICs 3 connected to the scan electrodes and the sustain electrodes are mounted on one lateral side of the PDP 10, and data side driver ICs 2 connected to the data electrodes are mounted on an upper or a lower side of the PDP 10. These drivers ICs 2 and 3 are connected through a connector 204 fitted thereto to a not-shown control circuit and power supply, so that the drivers ICs 2 and 3 apply voltages supplied from the control circuit and power supply, to the respective electrodes.
Referring to FIG. 9A, there is shown a partial sectional view illustrating one example of a prior art mounting structure for mounting the data side driver IC 2 on the PDP 10, which is disclosed by Japanese Patent Application Pre-examination Publication No. JP-A-10-260641. In this mounting structure, the data side driver IC 2 is constructed in the form of an IC package called a COF (chip on film), in which electrodes of an IC chip 40 are directly connected to an FPC (flexible printed circuit) 41, and a region including the:electrodes of the IC chip 40 is encapsulated with a resin 42. A back surface of the IC chip 40 is fixed by a heat conductive bonding agent 43 to a front face of an extension 14a of an aluminum reinforcement plate 14, outwardly projected from a periphery of the PDP 10 for protecting the glass plates 11 and 12 of the PDP 10. One end of the FPC 41 in the driver IC 2 is connected to a terminal 106a of the data electrodes formed on a front surface of the rear glass plate 12, and the other end of the FPC 41 is connected to an input printed circuit board 18 which is integrally-provided on a periphery of a front surface of the aluminum reinforcement plate 14. Incidentally, the reference number 19 designates a spacer inserted between the rear glass plate 12 and the aluminum reinforcement plate 14.
In addition, the above referred patent publication discloses another mounting structure shown in FIG. 9B, in which the IC chip 40 of the driver IC of the COF structure is mounted on a rear surface of the aluminum reinforcement plate 14. The FPC 41 is bent to extend over the peripheral edge of the aluminum reinforcement plate 14 so as to reach the rear surface of the periphery of the aluminum reinforcement plate 14, as shown in FIG. 9B. A front side end of the FPC 41 is connected to the terminal 106a of the data electrode formed on the front surface of the rear glass plate 12, and a rear side end of the FPC 41 is connected to the input printed circuit board 18 which is integrally provided on a rear surface of the aluminum reinforcement plate 14.
The above mentioned prior art mounting structures can be said to have been designed to pay importance to heat dissipation of the IC chip 40. Namely, as described in the above referred patent publication, in the color PDP, the heat generation of the driver IC 2 becomes remarkable because a load of the driver IC 2 increases with microminiaturization and the high density of the display cells. Therefore, it has become important to elevate the heat dissipation of the driver IC 2. By mounting the driver IC on the aluminum reinforcement plate 14 to cause the heat generated in the IC chip 40 to be immediately transferred to the aluminum reinforcement plate 14 and to be dissipated from a surface of the aluminum reinforcement plate 14, the above mentioned prior art mounting structure is intended to elevate the heat dissipation. On the other hand, in the prior art mounting structure shown in FIG. 9B proposed in the above referred patent publication for downsizing the PDP, by mounting the IC chip 40 on the rear surface of the aluminum reinforcement plate 14, it becomes unnecessary to extend the periphery of the aluminum reinforcement plate 14 outwardly from the periphery of the PDP 10, with the result that an outer scale of the PDP module is reduced.
The above mentioned mounting structures, however, since the IC chip 40 formed of a semiconductor such as silicon is directly fixed to the aluminum reinforcement plate 14 having a thermal expansion coefficient which is different from that of the semiconductor by one or more order of magnitude, when the driver IC 2 operates, a large heat stress acts on the IC chip 40 because of difference in heat expansion between the IC chip 40 and the aluminum reinforcement plate 14 caused by the heat generated in the IC chip 40, with the result that a crack occurs in the IC chip 40, so that reliability of the driver IC 2 lowers, and therefore, reliability of the PDP module 1 drops.
In the above mentioned mounting structures, furthermore, it is inevitable that the size of the PFC 41 in the COF structure, particularly, the length in a signal transmission direction from a signal input side to the terminal of the data electrode becomes long. Namely, in the mounting structure shown in FIG. 9A, since the IC chip 40 is fixed to the extension 14a of the aluminum reinforcement plate 14 extending outwardly from the periphery of the PDP 10, the FPC 14 is bent in a thickness direction by a step difference corresponding to a thickness of the rear glass plate 12, from the front surface of the rear glass plate 12 on which the terminals 106 of the data electrodes are formed, to the surface of the electrodes of the IC chip 40. However, since the FPC 41 is formed of a sheet formed of a resin such as polyimide and a circuit pattern of thin metal film integrally formed on the resin sheet, the FPC 41 cannot be bent with a small bend radius in a thickness direction. Therefore, a predetermined length is required for ensuring a necessary bending amount of the FPC 41. Furthermore, since the other end of the FPC 41 is connected to the input printed circuit board 18 which is then connected to an external circuit, the FPC 41 is required to have a length required to be connected to the input printed circuit board 18 and to allow the input printed circuit board 18 to be mounted on the FPC 41. On the other hand, in the structure shown in FIG. 9B, since the FPC 41 is bent to extend from the front surface and to reach the rear surface of the aluminum reinforcement plate 14, the FPC 41 becomes extremely long.
If the FPC 41 becomes long as mentioned above, the drive IC 2 becomes large in size, and the extension 14a of the aluminum reinforcement plate 14 correspondingly becomes long, with the result that the size of the PDP module 1 becomes large. In addition, since the FPC 41 is more expensive than a conventional printed circuit board, the cost of the driver IC 2 becomes high in proportion to an increase in the length of the FPC 41. In particular, in the color PDP intended to microminiaturize the display cells so as to increase the display cell density, the number of driver ICs 2 is inclined to increase more or more. If the number of driver ICs 2 incorporated in the PDP module 1 increases, the whole cost of the PDP module increases unneglectfully.
Accordingly, it is an object of the present invention to provide a flat panel display which has overcome the above mentioned problem of the prior art.
Another object of the present invention is to provide a flat panel display having an elevated heat dissipation effect of the driver ICs to elevate reliability of the driver ICs and having a reduced size and a lowered cost.
Still another object of the present invention is to provide a PDP apparatus having an elevated heat dissipation effect of the driver ICs to elevate reliability of the driver ICs and having a reduced size and a lowered cost.
The above and other objects of the present invention are achieved in accordance with the present invention by a flat panel display including a number of display cells formed and arranged on a transparent plate, wherein a driver integrated circuit for driving the display cells are tightly mounted on the transparent plate.
In an embodiment of the flat panel display, the transparent plate includes a display area where the display cells are formed and an extension extending outwardly from the display area, the driver integrated circuit being tightly mounted on the extension of the transparent plate. The driver integrated circuit includes a flexible printed circuit and an integrated circuit chip mounted on the flexible printed circuit, the integrated circuit chip including electrodes formed on an upper surface thereof and connected to the flexible printed circuit, a rear surface of the integrated circuit chip being tightly mounted on the transparent plate. In this case, cell electrodes for supplying a voltage to the display cells are formed on one surface of the transparent plate, and the driver integrated circuit is mounted on the one surface of the transparent plate and electrically connected to the cell electrodes through the flexible printed circuit.
In a preferred embodiment, a heat dissipating conductor film is integrally formed on the one surface of the transparent plate, and the integrated circuit chip is bonded on the heat dissipating conductor film. The heat dissipating conductor film can be formed of the same conducting film as that of the cell electrodes. In addition, a metal reinforcement plate can be backed to the transparent plate, the heat dissipating conductor film being heat-conductively coupled to the metal reinforcement plate through a heat conducting member.
Specifically, the transparent plate is constituted of a first glass plate of a pair of glass plates which are bonded to each other to constitute a plasma display panel, the driver integrated circuit being mounted on a portion of a surface of the first glass plate opposing to a second glass plate of the pair of glass plates. Preferably, the second glass plate is a front glass plate on which scan electrodes and sustain electrodes are formed as the cell electrodes, and the first glass plate is a rear glass plate on which data electrodes are formed as the cell electrodes. At least one end of the rear glass plate in an extending direction of the data electrodes has an extension extending beyond the front glass plate, and a driver integrated circuit for supplying a required voltage to the data electrodes is mounted on the extension of the rear glass plate. In addition, the driver integrated circuit can be packaged on the flexible printed circuit in the form of a tape carrier package structure or in the form of a chip on film structure.
With the above mentioned arrangement, since the driver integrated circuit is tightly mounted on the surface of the transparent plate such as the glass plate, when heat generates in the integrated circuit chip, a heat stress is suppressed, since the difference in thermal expansion coefficient between the semiconductor such as silicon constituting the integrated circuit chip and the glass plate is smaller, with the result that a crack is prevented from occurring in the integrated circuit chip. Since the integrated circuit chip is mounted on the surface of the transparent plate where cell electrodes are formed, the difference in height between the electrode surface of the integrated circuit chip and the cell electrode surface is reduced, so that the bending amount of the flexible printed circuit in the thickness direction can be minimized, and the size of the flexible printed circuit can be shortened. Therefore, the driver integrated circuit can be microminiaturized and the cost of the driver integrated circuit can be lowered. Since the heat generated in the driver integrated circuit can be effectively dissipated through the heat dissipating patterned conductor formed on the transparent plate, an overheating of the driver integrated circuit can be presented, and therefore, reliability of the driver integrated circuit can be elevated.
Japanese Patent Application Pre-examination Publication No. JP-A-09-292624 discloses a liquid crystal display apparatus in which a driver IC of the TCP (tape carrier package) structure is mounted on a glass plate of the liquid crystal display. This structure can be adopted because the heat generation of the driver IC in the liquid crystal display is remarkably small in comparison with that of the driver IC in the plasma display panel. Therefore, when this structure was applied to the plasma display panel with no modification, since the heat generation of the driver IC is remarkably large, the above mentioned problem cannot be satisfactorily overcome. JP-A-09-292624 also proposes that electrodes of an IC chip in the driver IC is connected to electrodes formed on the glass plate, by an anisotropic electrically conductive bonding agent. However, it is difficult to effectively transfer the heat generated in the IC chip through the anisotropic electrically conductive bonding agent to the glass plate. Even in this point, the above mentioned problem cannot be satisfactorily overcome by applying the technique disclosed in JP-A-09-292624 to the plasma display panel.
The above and other objects, features and advantages of the present invention will be apparent from the following description of preferred embodiments of the invention with reference to the accompanying drawings.